Baseline peripheral blood immune markers associated with clinical outcomes in patients with advanced breast cancer treated with trastuzumab deruxtecan

Background Trastuzumab deruxtecan (T-DXd) has demonstrated substantial clinical efficacy in patients with advanced breast cancer; however, predictive and prognostic biomarkers for treatment outcomes remain poorly defined. Host immune status has been reported to influence the efficacy of various systemic therapies, but its clinical significance in patients treated with T-DXd is not yet fully understood. Methods We conducted a retrospective, single-center study of patients with breast cancer who received T-DXd. Their baseline peripheral blood immune markers—including absolute lymphocyte count (ALC), neutrophil-to-lymphocyte ratio (NLR), and platelet-to-lymphocyte ratio—were evaluated prior to treatment initiation. Time-to-treatment failure (TTF) and overall survival (OS) were analyzed using Kaplan–Meier methods and Cox proportional hazards models. Results A total of 126 patients were included in the study. Univariate analyses showed that low ALC and high NLR were associated with shorter TTF and OS. In multivariate analyses adjusted for relevant clinical factors, low ALC and high NLR remained associated with shorter TTF and OS. Conclusions Baseline peripheral blood immune markers, particularly ALC and NLR, may be associated with clinical outcomes in patients with breast cancer treated with T-DXd. These readily available markers may have potential clinical utility and warrant further prospective validation.